Partial OpenSource products/licenses?

John Cowan jcowan at
Wed Oct 2 17:13:21 UTC 2002

James E. Harrell, Jr. scripsit:

> We have a product that we are considering publishing as open source. The
> product would be available for free download and use. Some features
> would be limited though, and only available if you purchase a commercial
> license. Thus, a portion of the code (containing a license key
> manager) would necessarily be closed-source in order to prevent
> someone from easily removing the license checking.

That way lies great pain and suffering for everyone.

Instead, I recommend you use the Mozilla Public License, and have two versions
of your product.  "ProductX Open" is fully open source under the MPL, which
basically allows people to create closed-source derivatives as long as they
reveal actual patches to the source (as opposed to additions).  "ProductX
Gold" is a derivative of ProductX Open, but is closed-source.  By using
the Netscape modification to the MPL (see the NPL), you can have patches
submitted to ProductX Open made reusable in ProductX Gold as well.

There is nothing preventing people from coding the Gold features into Open,
to be sure, but if you don't gouge your customers, they won't have much
incentive to do so.

John Cowan  jcowan at
"If I have seen farther than others, it is because I am surrounded by dwarves."
        --Murray Gell-Mann
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